This article refers to Force Plate (FP-BTA). The most common problem with the Force Plate is a bad load cell. If you are willing to replace the load cell(s) yourself using replacements from Vernier, follow these instructions.
Note that load cells in the force plate need to match for the force plate to work correctly. Vernier sends matched pairs of replacement load cells to customers for this repair. Do not replace a single load cell unless its number matches the other load cell in the force plate.
A load cell is bad if it is missing any of its pins, which may be found loose in the force plate housing. If this is not the case, the easiest way to tell if a load cell is bad is to take a good one (obtained from Vernier) and plug it into the circuit board in place of each suspect load cell.
Caution: If you have an older model Force Plate, the plugs on these bars are a weak spot; do not pull the plugs off by the wires. First try wiggling the wires and see if the readings change; you may just have a bad connection at this plug.
You will need: a Phillips screwdriver, an adjustable torque driver with a 1/8 inch hex bit, replacement load cell(s), and electrical tape.
First, unscrew the bottom six screws, as shown in the video below. Then use the adjustable torque driver at maximum torque to remove the 8 top screws. Important: if you do not use an adjustable torque driver you are likely to strip the screws. Open the Force Plate by removing the top. Remove the load cells. One at a time, hold each load cell in place as you attach it loosely to the bottom of the Force Plate. Be sure to leave the screws a bit loose, which will help when attaching the top plate.
Carefully attach the load cell wires to the circuit board as shown in the video. Tape down the wires to avoid pinching them during reassembly or later use. While you are inside the force plate, make sure the circuit board screws are snug. They have been known to come loose.
Once you have replaced the load cell(s), use the adjustable torque driver set to half the maximum torque to screw the top back on with the hex screws. Finally, tighten the bottom screws.
After reassembling the force plate, recalibrate the force plate using a 2-point calibration and a known weight. The bigger the weight, the better the calibration will be. Be sure to calibrate both ranges.